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How Rifle Scopes Work


Mounting a Rifle Scope
A scope on a Kettler Thirty-Aught-Six bolt-action rifle.
A scope on a Kettler Thirty-Aught-Six bolt-action rifle.
Georg Hanf/iStockphoto

Befo­re mounting the scope, you should hold your rifle in the position you'll be using while taking aim. Make sure it's a comfortable position -- you don't want to suffer a muscle cramp while you're preparing to fire. Pay attention to the way you position your head and neck. You'll want to mount your scope in a way that complements your posture.

The next step to mounting a scope to a rifle is to make sure you have all the equipment you'll need. That includes the scope, the unloaded rifle, the scope mount or base, the mounting rings and a set of tools including screwdrivers and an allen wrench. You should also work in a clean and well-lit environment. If your rifle isn't equipped for scope mounts, you may need to take it to a gunsmith first.

­There are several different styles of scope bases. They include the Weaver, Picatinny, Redfield/Leupold and clamp-on mounts among others. Some rifle manufacturers build a scope base directly in to the receiver -- the part of a rifle that houses the firing mechanism and ammunition feed system. You connect a scope base to a rifle with either clamps or screws, depending on the type of base. It's important to match your mounting rings to your base as well as your scope -- mismatched equipment can cause serious problems later.

Mounting rings are actually two-piece clamps. You attach the lower part of the rings directly to the scope base. The scope will rest in the lower half of the rings -- the upper half of the rings hold the scope in place. Mounting rings come in different heights -- the size of your scope's objective lens determines how tall your mounting rings need to be.

You'll need to secure your rifle in a gun vise before getting to work. Apply a light layer of oil to your rifle's receiver and the bottom of the base and rings. Follow the instructions for the type of base you've chosen. Use the right length of screw for each hole. Attach the base to the receiver, then the bottom half of the mounting rings to the base. Make sure all connections are snug and secure.

Take the rifle to an area where you can set up a target approximately 25 yards (22.9 meters) away. Remove the bolt on your rifle, install a bore sighter in the rifle's muzzle and look down the bore of the rifle. Adjust your scope to its highest magnification and place it onto the bottom half of your mounting rings. Fit the top rings over the scope and secure them loosely so that you can still adjust the scope's position. If you can position the scope's reticle to the approximate center of the bore sighter's reticle without tweaking the adjustment settings on the scope itself, you're in good shape. Otherwise, you may need to change the position of the mounting rings using the scope's knobs or screws and try again. It doesn't have to be perfect, but it should be close.

Next, we'll look at how to sight in a scope so that your aim is as accurate as possible.